1. Field of the Invention
The present invention relates to a plasma display panel (PDP). More specifically, the present invention relates to a PDP having enhanced discharge efficiency.
2. Discussion of the Related Art
Flat panel display devices, including liquid crystal displays (LCDs), field emission displays (FEDs), PDPs, and organic electroluminescence display devices, have been recently developed to improve upon the larger and heavier cathode ray tubes (CRT).
Among these flat panel display devices, large PDPs, which display characters or images using plasma generated by gas discharge, may be easily manufactured. A typical three-electrode surface discharge alternating current (AC) PDP will now be explained with reference to FIG. 13, FIG. 14 and FIG. 15.
FIG. 13 shows a partial exploded perspective view of a conventional three-electrode surface discharge AC PDP, and FIG. 14 shows a partial cross-section view of the PDP of FIG. 13 after fabrication.
Address electrodes 3 are formed on a rear substrate 1, and display electrodes 15, consisting of scan electrodes 11 and sustain electrodes 13, are formed on a front substrate 9. The scan electrodes 11 and the sustain electrodes 13 may have transparent electrodes 11a, 13a, which may be formed with indium tin oxide (ITO) or other like substances. The transparent ITO electrodes transmit visible rays very well, and are evenly formed on a large-sized panel with excellent affinity with neighboring materials. However, because the transparent electrodes 11a, 13a are highly resistant, metallic bus electrodes 11b, 13b are formed on the ITO electrodes 11a, 13a to enhance electrical conductivity.
A first dielectric layer 17 covers the address electrodes 3, and a second dielectric layer 19 covers the display electrodes 15. A protective layer 21, which is typically formed of magnesium oxide (MgO), may cover the second dielectric layer 19. The scan and sustain electrodes 11, 13 are arranged to cross the address electrodes 3. Barrier ribs 5, which may be formed in between and in parallel to the address electrodes 3, are formed on the first dielectric layer 17 to define and prevent cross talk between discharge cells.
An intersection of an address electrode 3 with a display electrode pair 15 defines a discharge cell, which may be filled with a discharge gas such as a Ne—Xe mixed gas.
With above-structured PDP, applying a driving voltage Va to the address electrodes 3 and the scanning electrodes 11 generates an address discharge between the electrodes, thereby forming wall charges within a discharge cell. At this time, (+) and (−) electric charges (wall charges) corresponding to a polarity of the scan or sustain electrodes 11, 13 are charged in the second dielectric layer 19. The wall charges may form a space voltage (wall voltage Vw) between the scan and sustain electrodes 11 and 13, which functions to select the discharge cells.
If a discharge sustain voltage Vs is applied across a pair of scan and sustain electrodes 11, 13, it may be summed with the wall voltage Vw. When the total voltage (Vs+Vw) exceeds a firing voltage Vf, a sustain discharge is performed in the discharge cell, thereby exciting the discharge gas. The excited discharge gas generates ultraviolet rays, which in turn excite phosphor layers 7 to generate visible rays and display desired images.
Before an address period to select these discharge cells, a reset period may be performed to erase wall charges from a previous sustain discharge. Traditionally, in the reset period of a PDP, (+) charges accumulate on a portion of the first dielectric layer 17 corresponding to the address electrode 3, and (−) charges accumulate on a portion of the second dielectric layer 19 corresponding to the scan electrode 11. The charges may then be erased or set. As a result, an address discharge may be performed smoothly.
FIG. 14 and FIG. 15 show plasma discharge paths and wall charge distribution at sustain discharge in a discharge cell of a PDP operated as above.
Referring to FIG. 14, plasma discharges are generated in the gap G between the scan and sustain electrode 11, 13 to spread in the discharge cell. The discharge intensity decreases away from the gap G. Accordingly, discharge paths to emit vacuum ultraviolet rays may be limited to paths {circle around (1)}, {circle around (2)}, {circle around (3)} of FIG. 14.
A conventional PDP may have low discharge efficiency due to a short sustain discharge path and because the discharge may be localized at the center portion of the gap G.
Also, referring to FIG. 15, the wall charge distribution curve, which shows wall charges charged on the second dielectric layer 19, has a minimum value at the gap G, and a maximum value at about 50 μm to about 100 μm from the gap G toward the scan and sustain electrodes 11, 13. That is, the charge distribution curve tends to reduce the amount of wall charge at the periphery of the gap G. With the above-structured conventional PDP, the wall discharge may be produced locally at the second dielectric layer 19. Therefore, the second dielectric layer 19 may not be used efficiently.